How do I taper a cylindrical object in blender?
That should be easy. Add a lattice to your scene. A basic one with just 8 vertices is best. Scale it in world space to match your engraved form. Don't do it in edit mode! Now, when the lattice object enwraps your engraved form completely, add a lattice modifier to it. Now, if you move a vertex of your lattice in edit mode, the mesh deforms accordingly.

Select the top four vertices of the lattice, press Shift+S and click Cursor To Selected. Now, you can simply scale these vertices, until your engraved form match the form of your cylinder.